"Bruno Luong" <b.luong@fogale.findmycountry> wrote in message <k7vfli$da4$1@newscl01ah.mathworks.com>...> "Matt J" wrote in message <k7ulhl$iod$1@newscl01ah.mathworks.com>...> > >In fact, the sparse matrix multiplication is probably even handicapped relative to accumarray, since it has to search through x for the appropriate x(J), > > There is no such step in sparse multiplication.=============

Meaning that y=A*x is generated by looping over columns of A instead of rows? Even if so, how would that explain the speed difference?